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NOUS41 KWBC 271916

Service Change Notice 15-04
National Weather Service Headquarters Washington DC
217 PM EST Tue Jan 27 2015

TO:      Subscribers:
         -Family of Services
         -NOAA Weather Wire Service
         -Emergency Managers Weather Information Network
         Other NWS Partners and NWS employees

FROM:    David Novak
         Director, Weather Prediction Center

SUBJECT: Downscaled version of WPC Probabilistic Winter
         Precipitation Forecasts (GRIB only) Effective
         February 26, 2015

Effective Thursday, February 26, 2015, at 1800 Coordinated
Universal Time (UTC), the National Centers for Environmental
Prediction (NCEP) Weather Prediction Center (WPC) will add a
downscaled version of the Probabilistic Winter Precipitation
Forecasts (PWPF) of snow and ice accumulation.

Currently smooth probabilistic information is provided on the
National Digital Forecast Database (NDFD) 5 km horizontal
resolution grid. WPC will add a downscaled version of the PWPF
data on the 2.5 km NDFD grid. The addition only affects GRIB
data and is not reflected in web or GIS products. The addition
is based on numerous stakeholder requests and is part of
continual product improvement. The downscaling uses monthly
PRISM data. Enhanced product detail is most evident in the
western United States, with lessor effects in the East.

Current 5 km PWPF snow and ice forecasts in GRIB2 format are
available at:

The additional downscaled PWPF snow and ice forecasts in GRIB2
format will be available after 1800 UTC, February 26, 2015, at:

No changes will be made to WMO headers or web products; however,
grid file sizes for the full PWPF suite will increase from
approximately 2 mb to as much as 100 mb in aggregate size.

For more information, please contact:

National Service Change Notices are online at:

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